An obsidian bar is a bar of obsidian, smithed from obsidian shards. 80 Smithing and completion of The Brink of Extinction are required to smith obsidian bars. The shards may only be obtained from the Fight Cauldronminigame, accessible upon completing The Brink of Extinction, as drops from the TokHaar monsters within. 12 obsidian shards are required to smelt an obsidian bar, and 50 Smithing experience is granted.

Obsidian bars may be smithed at any anvil into obsidian armour, level 60 armour that is exceptionally useful against TzHaar and TokHaar monsters, but not useful against any other opponents. Smithing an obsidian item will grant 75 experience per bar used, for a total of 125 experience for smelting and smithing each obsidian bar, the same amount as a rune bar. The assist system does work when smithing Obsidian equipment. Portable forges work when smithing obsidian equipment on saving a bar.